StandardScannerExecutor will stuck on ghost vertices

Nobody has claimed this yet.

It seems second condition check for vertex existing - not ghost vertex
```
if (currentResults[i]!=null && currentResults[i].key.equals(key)) {
assert query.equals(currentResults[i].query);
entries = currentResults[i].entries;
currentResults[i]=null;
}
```
https://github.com/JanusGraph/janusgraph/blob/master/janusgraph-core/src/main/java/org/janusgraph/diskstorage/keycolumnvalue/scan/StandardScannerExecutor.java#L167

But if is it ghost `currentResult[i]` stay filled and it lead to queue exhaust

```
for (int i = 0; i < numQueries; i++) {
if (currentResults[i]!=null) continue;
```

It lead to any scanner job including `IndexRepairJob`, `IndexRemoveJob`, `VertexProgramScanJob` may partially work. Issue https://github.com/JanusGraph/janusgraph/issues/1389 partially related too

GhostRemoveJob can help if will run before any scanner job, but can't due issue https://github.com/JanusGraph/janusgraph/issues/1749

I think second way to fix that issue just skip ghost vertice during scan

https://github.com/JanusGraph/janusgraph/blob/master/janusgraph-core/src/main/java/org/janusgraph/diskstorage/keycolumnvalue/scan/StandardScannerExecutor.java#L167
```
if (currentResults[i]!=null && currentResults[i].key.equals(key)) {
assert query.equals(currentResults[i].query);
entries = currentResults[i].entries;
}
currentResults[i] = null;
```

Workaround, remove ghost vertex before start main job

```
JanusGraphManagement.IndexJobFuture ghostRemover =
graph.getBackend().buildEdgeScanJob()
.setJob(new GhostVertexRemover(graph))
.execute();
try {
logger.info("GhostVertexRemover statistics: {},{},{}",
ghostRemover.get().getCustom(REMOVED_VERTEX_COUNT),
ghostRemover.get().getCustom(REMOVED_RELATION_COUNT),
ghostRemover.get().getCustom(SKIPPED_GHOST_LIMIT_COUNT));
} catch (InterruptedException | ExecutionException e) {
throw new RuntimeException(e);
}
```

Start in janusgraph-core/src/main/java/org/janusgraph/diskstorage/keycolumnvalue/scan/StandardScannerExecutor.java around line 167 and trace how ghost vertices leave currentResults occupied. Review the affected scanner jobs, including IndexRepairJob, IndexRemoveJob, and VertexProgramScanJob, and confirm that scanning no longer exhausts its queue or partially processes work when ghost vertices are present.

Written by the indexing model from the issue text.